This invention relates in general to mass transfer and heat exchange columns and, more particularly, to a method and apparatus to improve vapor distribution in such columns.
Vapor and liquid interaction is required in many types of mass transfer and heat exchange processes. Typically, the vapor stream is introduced to a column below a region containing trays or a random or structured packing while the liquid stream is introduced into the column above the trays or packing. The vapor and liquid streams then flow in countercurrent relation through the region, with the tray or packing serving to distribute the downwardly flowing liquid stream over a larger surface area to enhance the interaction with the upwardly flowing vapor stream.
In order to increase the efficiency of the mass transfer or heat exchange taking place between the vapor and liquid streams, it is important that the vapor be uniformly distributed across the horizontal cross-section of the column, particularly at the lower vapor-liquid interface where the vapor enters the packing. When the vapor is introduced to the column below the packing, the velocity of the vapor can prevent the desired horizontal distribution of the vapor prior to its entry into the packing. In order to improve the vapor distribution, deflectors have been positioned in some columns in the flow path of the vapor to deflect the vapor in a plurality of directions. One example of such a deflector is a V-shaped deflector which is positioned at the vapor inlet to split the vapor stream into two streams flowing in opposite directions. This deflector is of a simple design and performs adequately in many installations that tolerate some maldistribution of the vapor stream.
Another example of a conventional vapor distributor known as a vapor horn is disclosed in U.S. Pat. No. 5,106,544. The vapor horn disclosed in that patent comprises an annular housing which is open at the bottom. The vapor horn contains a plurality of vanes which extend upwardly at progressively greater distances into the housing through the open bottom for causing downward deflection of the circumferentially flowing vapor stream. The downwardly deflected vapor is then said to rise in a uniform manner into a packing bed which is positioned radially inwardly from the vapor horn.
While conventional vapor distributors can function satisfactorily in many applications, a need has arisen for an improved vapor distributor which will provide a more uniform distribution of vapor across the horizontal cross-section of a mass transfer or heat exchange column.